Method for ammoxidation of paraffins and catalyst system therefor

ABSTRACT

Disclosed is ammoxidation of C 3  to C 5  acyclic alkanes with NH 3  and O 2  using (1) a mole ratio of alkane:NH 3  in the range from 2 to 16 and a mole ratio of alkane:O 2  in the range 1 to 10 and (2) a mixture of particulate catalyst compositions, the first being especially effective to promote formation of an unsaturated nitrile and an olefin from the paraffin, and the second catalyst composition being especially effective to promote the conversion of the olefin to the unsaturated mononitrile. Catalyst compositions useful in the process are also disclosed.

this is a division of application Ser. No. 204,475, filed June 9, 1988,now U.S. Pat. No. 4,837,191, which in turn is a continuation-in-part ofapplication Ser. No. 194,665, filed May 16, 1988 now U.S. Pat. No.4,843,055.

This invention relates to an improved process for the catalyticammoxidation of paraffins containing from 3 to 5 carbon atoms toα,β-unsaturated mononitriles, especially paraffins containing 3 to 4carbon atoms. Most important is the ammoxidation of isobutane tomethacrylonitrile and, especially, of propane to acrylonitrile.

Because of the price differential between propylene and propane aneconomic incentive exists for the development of a viable catalyticprocess for conversion of propane to acrylonitrile.

Earlier attempts in the prior art to develop an efficient process forthe ammoxidation of propane to acrylonitrile produced eitherinsufficient yields or processes that necessitated adding halogenpromoters to the feed. The latter procedure would require not onlyreactors made of special corrosion resistant materials, but also thequantitative recovery of the promoter. The added costs thus eliminatedthe advantage of the propane/propylene price differential.

It is thus an object of the present invention to provide an improvedprocess for the ammoxidation of paraffins to unsaturated mononitriles.

It is a further object of the invention to provide new catalyst systemsfor such process.

Still another object is to provide an improved catalytic ammoxidationprocess for making unsaturated mononitriles from lower paraffins withoutthe use of halogen promoters.

Other objects, as well as aspects, features and advantages, of thepresent invention will become apparent from a study of the accompanyingdisclosure and the claims.

The foregoing and other objects of the present invention are achieved bythe process of the present invention. There are two main features of thepresent process invention. The first of these is the use of an excess ofthe alkane feed with relation to NH₃ and molecular oxygen. The secondfeature, which is used in combination with the high ratio of the C₃ toC₅ paraffin to NH₃ and O₂, is that a combination, i.e., a mixture, ofcatalysts is employed, the first catalyst composition being especiallyeffective to promote formation of an unsaturated mononitrile and anolefin from the paraffin, and the second catalyst composition beingespecially effective to promote the conversion of the olefin to theunsaturated nitrile. Such mixture is the subject of the compositionclaims herein.

In the present application "paraffin" designates an acyclic paraffin.

British Patent Specifications 1,336,135 and 1,336,136 disclose the useof high ratios of propane or isobutane to ammonia and oxygen, but onlysingle ammoxidation catalysts are used, and the yields of acrylonitrileare extremely poor. U.S. Pat. No. 3,860,534 also discloses use of suchhigh ratios, using a catalyst containing only V and Sb oxides. However,after the catalyst is calcined, it is washed for 24 hours with water anddried, a laborious procedure. A. N. Shatalova et al. in Neftekhiniya 8,No. 4, 609-612 (1968), describe the reaction of propane with oxygen andammonia using a large excess of propane and a mixture of two catalysts,one of which is described as oxides of metals having dehydrogenatingcharacteristics at 550° and 600° C. At 500° C. little or noacrylonitrile was produced. Rather large amounts of propionitrile andacrolein were made per mole of acrylonitrile produced. The per passconversion of propane to acrylonitrile was generally 2-4 percent withselectivity to acrylonitrile being from 12 to 33 percent.

In the present process when applied to propane ammoxidation a smallamount of propylene is produced in relation to the unreacted propane inthe effluent. Such propane effluent containing propylene in the amountof up to 8 mole percent, but usually no more than 6 mole percent, of theamount of propane plus propylene can comprise the substrate feed to thepresent process. And in general the C₃ to C₅ alkene feed to the processcan contain one or more C₃ to C₅ olefins. The C₃ to C₅ olefin content ofthe feed to the present ammoxidation process can contain from zero to 8mole percent of such olefin(s), based on the moles of C₃ to C₅ paraffinplus olefins fed, and this feed can be from any source. Although largeramounts of C₃ to C₅ olefins may be present in the substrate paraffinfeed, usual amounts are as stated, and the usual olefin is thatcorresponding to the particular paraffin fed to the reaction zone of thepresent process.

According to one aspect of the present invention there is provided aprocess for the ammoxidation of a C₃ to C₅ paraffin to anα,β-unsaturated mononitrile which comprises contacting in a reactionzone said paraffin in the vapor phase in admixture with ammonia,molecular oxygen, and optionally an inert gaseous diluent, with anintimate particulate mixture of a first catalyst composition and asecond catalyst composition, said feed to the reaction zone containing amole ratio of paraffin:NH₃ in the range from 2 to 16 (usually 3-7), anda mole ratio of paraffin to O₂ in the range from 1 to 10 (usually1.5-5), said first catalyst composition being 0-99 weight percent of adiluent/support and 100-1 weight percent of a catalyst having oxygen andthe cation components in the proportions indicated by the empiricalformula:

    Bi.sub.a V.sub.b L.sub.l M.sub.m T.sub.t O.sub.x,          formula (1)

wherein

L is one or more of K, Cs, Rb and Tl;

M is one or more of Mo, W, Cr, Ge, Sb, Sn, P, Pb and B;

T is one or more of Zn, Nb, Ta, Fe, Co, Ni Cu, Mn, Ti and rare earths;

a=1-25

b=1-50

l=0-1, usually 0-0.2

m=0.1-20

t=0-20

x is determined by the oxidation state of the other elements in thecatalyst,

(a+b):(l+m+t)=20:1 to 1:5

a:b=1:5-5:1, usually 1:3-3:1,

with the proviso that the atomic ratio of Mo:V is zero to <10; saidsecond catalyst composition being 0-99 weight percent of adiluent/support and 100-1 weight percent of a catalyst having oxygen andthe cation components in the proportions indicated by the empiricalformula:

    Bi.sub.k Fe.sub.l Mo.sub.12 V.sub.v D.sub.d E.sub.e F.sub.f G.sub.g O.sub.x formula ( 2)

where

D is one or more of an alkali metal, Sm, Ag

E is one or more of Mn, Cr, Cu, Zn, Cd, La,

F is one or more of P, As, Sb, Te, W, B, Sn, Pb, Se

G is one or more of Co, Ni, alkaline earth metal and

k is 0.1-12, l is 0.01-12, v is 0-0.5, d is 0-0.5, e is 0-10, f is 0-10,g is 0-12, v+k+l+d+e+f+g≦24, and x is a number determined by the valencerequirements of the other elements present, wherein the weight ratio insaid mixture of said first catalyst composition to said second catalystcomposition is in the range of 0.001 to 2.5.

By "particulate mixture" as used herein is meant a mixture of solidparticles or subdivided pieces of the first catalyst composition withseparate and distinct solid particles of the second catalystcomposition. The particles are often of a size used in fluidized bedreactors, say about 40 to 90 microns, but of course larger particles ofcatalyst can be employed for use in fixed or gravity flowing catalystbeds.

"Rare earths" as used herein means atomic numbers 57 through 71.

In the present process in all its embodiments the ratio of O₂ to NH₃ fedto the reaction zone is usually in the range from 1 to 10 (more often1-5) and the ratio of inert gaseous diluent to paraffin is usually inthe range zero to 5 (more often zero to 3).

The diluent or support for either catalyst composition is a refractorymetal oxide or mixture, such as silica, silica-alumina, etc.

In the usual practice of the present invention the catalystsupport/diluent for the catalyst of formula (1) is not an oxide of anelement named in formula (1). Further, in the usual practice of theinvention the catalyst support/diluent for the catalyst of formula (2)is not an oxide of an element named in formula (2).

In the catalyst compositions of the invention the catalyst empiricalformulas (1) and (2) do not, of course, connote any particular chemicalcompound, nor indicate whether the elements are present as a mixture ofindividual oxides or as a complex oxide or oxides, or what separatecrystalline phases or solid solutions may be present. Similarly, thedesignation of certain oxides, such as "silica" or "alumina" or SiO₂ orAl₂ O₃, as supports or diluents is merely in accordance with conventionin the inorganic oxide catalyst art, and such designations refer tocompounds often regarded as supports in the catalyst art. Suchdesignations, however, do not mean that the element involved is actuallypresent as a simple oxide. Indeed, such elements may at times be presentas a complex oxide with one, more than one, or all of the elements informula (1) or formula (2), which complex oxides form during theprecipitation or agglomeration, drying and calcining process forpreparing the catalyst composition.

The process of the invention is especially useful in the ammoxidation ofpropane or isobutane.

In the preparation of the catalyst compositions of formula (1) orformula (2) the metal oxides can be blended together or can be formedseparately and then blended or formed separately or together in situ.Promoter oxides are conveniently incorporated into thebismuth-iron-molybdenum based catalyst by blending into the gel beforecalcining or by blending into the oven-dried base catalyst beforecalcining. A useful manner of incorporating promoter elements is bychoosing a water-soluble salt of the promoter element, forming anaqueous solution of the salt, and mixing the solution with a solution ora suspension of the base elements or salts thereof. Optionally, thepromoter elements may be incorporated by the use of soluble complexsalts or compounds with the desired base elements which upon calcinationwill yield the desired ratio of the elements in the finished catalyst.

Bismuth may be introduced into the catalyst as an oxide or as any saltwhich upon calcination will yield the oxide. Most preferred are thewater-soluble salts which are easily dispersible within the catalyst andwhich form stable oxides upon heat-treating. The most preferred salt forintroducing bismuth is bismuth nitrate.

To introduce the iron component into the catalysts one may use anycompound of iron which, upon calcination, will result in the oxides. Aswith the other elements, water soluble salts are preferred for the easewith which they may be uniformly dispersed within the catalyst. Mostpreferred is ferric nitrate. Cobalt and nickel are similarly introduced.

To introduce the molybdenum component any molybdenum oxide such as thedioxide, trioxide, pentoxide or sesquioxide may be used; more preferredis hydrolyzable or decomposable molybdenum salt such as molybdenumhalide. A preferred starting material is ammonium heptamolybdate.

Other variations in starting materials will suggest themselves to oneskilled in the art, particularly when the preferred starting materialsmentioned hereinabove are unsuited to the economics of large-scalemanufacture. In general, any compounds containing the desired catalystcomponents may be used provided that they result, upon heating to atemperature within the range disclosed hereinafter, in the oxides of theinstant catalyst.

These catalyst compositions can conveniently be prepared by slurrytechniques wherein an aqueous slurry containing all of the elements inthe objective catalyst is produced. In any event, a solution or slurrycontaining all of the elements of the catalyst is formed. This isfollowed by evaporation, drying and then calcining the product in amolecular oxygen-containing atmosphere, such as air, at from 350° to700° or 750° C., usually 400° to 650° C. The length of the calcinationperiod may range from 30 minutes to 12 hours, but satisfactory catalystcompositions are usually obtained by calcination at such temperaturesfor a period of from 1 to 5 hours. Until calcination the compositionsare not catalysts but are merely precatalysts with little or nocatalytic activity. Liquids other than water, such as C₁ to C₈ alcoholscan also be used to form the precatalyst slurry.

In the ammoxidation of the present invention, the reaction is carriedout in the gas phase by contacting a mixture of the paraffin, ammoniaand molecular oxygen, and inert diluent, if any, conveniently in a fixedbed of the catalyst mixture, or a gravity flowing bed, a fluidized bedor a fast transport reactor mode.

Examples of inert diluents useful in the reaction are N₂, He, CO₂, H₂ Oand Ar.

The reaction temperature range can vary from 350° to 700° C., but isusually 430° to 520° C. The latter temperature range is especiallyuseful in the case of propane ammoxidation to acrylonitrile.

The average contact time can often be from 0.01 to 10 seconds, but isusually from 0.02 to 10 seconds, more usually from 0.1 to 5 seconds.

The pressure of the reaction usually ranges from 2 to 45 psia. Mostoften, pressure is somewhat above atmospheric.

The following examples of the invention are exemplary and should not betaken as in any way limiting.

EXAMPLE 1

A solution containing chromium nitrate and bismuth nitrate dissolved indilute nitric acid was mixed with a solution containing ammoniummetavanadate and ammonium heptamolybdate dissolved in hot water. Silicasol and alumina sol were added to this and the slurry was evaporated todryness over a hot plate. The dry material was heat treated at 290° C./3hours, 425° C./3 hours, and 610° C./3 hours. The composition of thecatalyst was 50% BiV₀.7 Mo₀.5 CrO_(x) +25% SiO₂ +25%Al₂ O₃.

EXAMPLE 2

Ammonium heptamolybdate was dissolved in water. Silica sol was added,followed by CrO₃. Iron nitrate was melted on a hotplate with a smallamount of water. Then, in order, were added manganese, bismuth, cobaltand nickel nitrates, forming a solution that was added to the Mo--Cr--Sisolution previously prepared, forming a slurry which was heated on ahotplate with stirring until it started to thicken. It was then dried at120° C., heated 3 hours at 290° C. and 3 hours at 425° C.

The composition was then ground to 20-35 mesh and heated for 3 hours at610° C. The catalyst composition was 50% Ni₂.5 Co₄.5 Fe₂ MnBiCr₀.5Mo₁₃.2 O_(x) +50% SiO₂

EXAMPLE 3

A catalyst having the empirical composition 50% Ni₂.5 Co₄.5 Fe₂ MnCr₀.5BiMo₁₀ O_(x) +50% SiO₂ was made in the manner of Example 2.

EXAMPLE 4

Ammonium heptamolybdate was dissolved in water. Silica sol was added,followed by CrO₃. Iron nitrate was melted on a hotplate with a smallamount of water. Then, in order, were added manganese, bismuth,magnesium and nickel nitrates, forming a solution that was added to theMo--Cr--Si solution previously prepared, forming a slurry which washeated on a hotplate with stirring until it started to thicken. It wasthen dried at 120° C., heated 3 hours at 290° C. and 3 hours at 425° C.

The composition was then ground to 20-35 mesh and heated for 3 hours at610° C. the catalyst composition was 50% Mg₂ Ni₅ Fe₂ MnBiCr₀.5 Mo₁₃.2O_(x) +50% SiO₂.

EXAMPLE 5

69.92 g of (NH₄)₆ Mo₇ O₂₄.4H₂ O were dissolved in 200 cc of warm water.222.27 g of a 40 wt% silica sol was added, then 3.0 g of CrO₃, formingan orange solution. Then 24.24 g of Fe(NO₃)₃.9H₂ O were melted on ahotplate with a small amount of water. Then, in order listed, 10.74 g ofMn(NO₃)₂ (a 50 wt% solution in water), 14.55 g Bi(NO₃)₃.5H₂ O, 39.29 gCo(NO₃)₂.6H₂ O and 21.81 g Ni(NO₃)₂.6H₂ O were added, forming a darkbrown solution. The latter solution was added to the orange solution,forming a pale yellow slurry, which was heated on a hotplate withconstant stirring until it started to thicken; it was then dried at 120°C., then heated at 290° C. for 3 hours and 425° C. for 3 hours, thenground to about 20-35 mesh size. A portion of the catalyst was thencalcined by heating at 610° C. for 3 hours. The catalyst composition was50 wt% Ni₂.5 Co₄.5 Fe₂ MnBiCrMo₁₃.2 O_(x) +50 wt% SiO₂.

EXAMPLE 6

Ammonium heptamolybdate was dissolved in water. The ammoniummetatungstate was added, followed by silica sol and then CrO₃. Ironnitrate was melted on a hotplate with a small amount of water. Then, inorder, were added manganese, bismuth, cobalt and nickel nitrates,forming a solution that was added to the Mo--Cr--Si solution previouslyprepared, forming a slurry which was heated on a hotplate with stirringuntil it started to thicken. It was then dried at 120° C., heated 3hours at 290° C. and 3 hours at 425° C.

The composition was then ground to 20-35 mesh and heating for 3 hours at610° C. The catalyst composition was 50% Co₄.5 Ni₂.5 Fe₂ BiMnCr₀.5 Mo₁₂W₁.2 O_(x) +50% SiO₂.

EXAMPLE 7

69.92 g of (NH₄)₆ Mo₇ O₂₄.4H₂ O were dissolved in 200 cc of warm waterand 216.57 g of a 40 wt% silica sol was added, forming a first solution.Then 24.24 g of Fe(NO₃)₃.9H₂ O were melted on a hotplate with a smallamount of water. Then, in order listed, 10.74 g of Mn(NO₃)₂ (a 50 wt%solution in water), 14.55 g Bi(NO₃)₃.5H₂ O, 39.29 g Co(NO₃)₂.6H₂ O and21.81 g Ni(NO₃)₂.6H₂ O were added, forming a dark brown solution. Thelatter solution was added to the first solution, forming a slurry, whichwas heated on a hotplate with constant stirring until it started tothicken; it was then dried at 120° C., then heated at 290° C. for 3hours and 425° C. for 3 hours, then ground to about 20-35 mesh size. Aportion of the catalyst was then calcined by heating at 610° C. for 3hours. The catalyst compositions was 50 wt% Co₄.5 Ni₂.5 Fe₂ MnBiMo₁₃.2O_(x) +50% SiO₂ support.

EXAMPLE 8

Ammonium heptamolybdate was dissolved in water. Silica sol was added,followed by CrO₃. Iron nitrate was melted on a hotplate with a smallamount of water. Then, in order, were added manganese, bismuth, cobaltand nickel nitrates, forming a solution that was added to the Mo--Cr--Sisolution previously prepared, forming a slurry which was heating on ahotplate with stirring until it started to thicken. It was then dried at120° C., heated 3 hours at 290° C. and 3 hours at 425° C.

The composition was then ground to 20-35 mesh and heated for 3 hours at610° C. The catalyst composition was 50% Ni₂.5 Co₄.5 Fe₂ MnBiCr₀.5 Mo₁₂O_(x) +50% SiO₂.

EXAMPLE 9

Ammonium heptamolybdate was dissolved in water. The ammoniummetatungstate was added, followed by silica sol and then CrO₃. Ironnitrate was melted on a hotplate with a small amount of water. Then, inorder, were added manganese, bismuth, cobalt and nickel nitrates,forming a solution that was added to the Mo--Cr--Si solution previouslyprepared, forming a slurry which was heated on a hotplate with stirringuntil it started to thicken. It was then dried at 120° C., heated 3hours at 290° C. and 3 hours at 425° C. The composition was then groundto 20-35 mesh and heated for 3 hours at 610° C. The catalyst compositionwas 50% Co₄.5 Ni₂.5 Fe₂ BiMnCr₀.5 Mo₁₀ W₂ O_(x) +50% SiO₂.

EXAMPLE 10

Ammonium heptamolybdate was dissolved in water. Silica sol was added,followed by CrO₃. Iron nitrate was melted on a hotplate with a smallamount of water. Then, in order, were added manganese, bismuth, cobalt,nickel and potassium nitrates, forming a solution that was added to theMo--Cr--Si solution previously prepared, forming a slurry which washeated on a hotplate with stirring until it started to thicken. It wasthen dried at 120° C., heated 3 hours at 290° C. and 3 hours at 425° C.

The composition was then ground to 20-35 mesh and heated for 3 hours at610° C. The catalyst composition was 50% K₀.05 Ni₂.5 Co₄.5 Fe₂ MnBiCr₀.5Mo₁₂ O_(x) +50% SiO₂.

EXAMPLE 11

Ammonium heptamolybdate was dissolved in water. Silica sol was added,followed by CrO₃. Iron nitrate was melted on a hotplate with a smallamount of water. Then, in order, were added manganese, bismuth, cobalt,nickel and potassium nitrates, forming a solution that was added to theMo--Cr--Si solution previously prepared, forming a slurry which washeated on a hotplate with stirring until it started to thicken. It wasthen dried at 120° C., heated 3 hours at 290° C. and 3 hours at 425° C.

The composition was then ground to 20-35 mesh and heated for 3 hours at610° C. The catalyst composition was 50% K₀.05 Ni₂.5 Co₄.5 Fe₂ MnBiCr₀.5Mo₁₃.2 O_(x) +50% SiO₂.

EXAMPLE 12

A catalyst having the composition 50% Fe₆.6 Bi₄.2 P₁.2 Mo₁₂ O_(x) +50%SiO₂ was made as follows: 63.56 g of ammonium heptamolybdate wasdissolved in 200 ml of water. 4.15 g of 85% H₃ PO₄ was added to thissolution and then 248.85 g of a 40 wt.% silica sol.

In a separate beaker 80 g of ferric nitrate was wetted with about 15 mlof water at about 60° C. Then 61.12 g of bismuth nitrate was dissolvedin this solution. The resulting solution was added slowly with stirringto the other mixture, and the resulting slurry was heated with stirringto remove excess water. When it no longer could be stirred it was driedovernight at about 120° C., heated 3 hours at 290° C. and then 3 hoursat 425° C. It was ground and screened to 20-35 mesh and a portioncalcined at 610° C. for 3 hours.

EXAMPLE 13

A catalyst having the composition 50% K₀.05 Fe₆.6 Bi₄.2 P₁.2 Mo₁₂ O_(x)+50% SiO₂ was made as follows: 63.56 g of ammonium heptamolybdate wasdissolved in 200 ml of water 4.15 g of 85% H₃ PO₄ was added to thissolution and then 249.02 g of a 40 wt. % silica sol.

In a separate beaker 80 g of ferric nitrate was wetted with about 15 mlof water at about 60° C. Then 61.12 g of bismuth nitrate was dissolvedin this solution, followed by 1.52 g of a 10 wt% solution of KNO₃. Theresulting solution was added slowly with stirring to the other mixture,and the resulting slurry was heated with stirring to remove excesswater. When it no longer could be stirred it was dried overnight atabout 120° C., heated 3 hours at 290° C. and then 3 hours at 425° C. Itwas ground and screened to 20-35 mesh and a portion calcined at 610° C.for 3 hours.

EXAMPLE 14

A catalyst having the composition 50% Fe₆.6 Bi₄.2 P₁.2 Mo₁₀ O_(x) +50%SiO₂ was made as follows: 52.97 g of ammonium heptamolybdate wasdissolved in 200 ml of water. 4.15 g of 85% H₃ PO₄ was added to thissolution and then 227.26 g of a 40 wt. % silica sol.

In a separate beaker 80 g of ferric nitrate was wetted with 15 ml ofwater at about 60° C. Then 61.12 g of bismuth nitrate was dissolved inthis solution. The resulting solution was added slowly with stirring tothe other mixture, and the resulting slurry was heated with stirring toremove excess water. When it no longer could be stirred it was driedovernight at about 120° C., heated 3 hours at 290° C. and then 3 hoursat 425° C. It was ground and screened to 20-35 mesh and a portioncalcined at 610° C. for 3 hours.

EXAMPLE 15

A catalyst having the composition 50% Fe₆.6 Bi₄.2 P₁.2 Mo₈ O_(x) +50%SiO₂ was made in the same manner as Example 14.

EXAMPLE 16

A catalyst having the composition 50% Fe₆.6 Bi₄.2 P₁.2 Mo₁₀ W₂ O_(x)+50% SiO₂ was made as follows: 52.97 g of ammonium heptamolybdate wasdissolved in 200 ml of water. 16.37 g of ammonium metatungstate (85%WO₃) was then added, followed by 4.15 g of 85% H₃ PO₄ and then 262.03 gof a 40 wt. % silica sol.

In a separate beaker 80 g of ferric nitrate was wetted with about 15 mlof water at about 60° C. Then 61.12 g of bismuth nitrate was dissolvedin this solution. The resulting solution was added slowly with stirringto the other mixture, and the resulting slurry was heating with stirringto remove excess water. When it no longer could be stirred it was driedovernight at about 120° C., heated 3 hours at 290° C. and then 3 hoursat 425° C. It was ground and screened to 20-35 mesh and a portioncalcined at 610° C. for 3 hours.

EXAMPLE 17

Ammonium heptamolybdate was dissolved in water. Silica sol was added,followed by CrO₃. The silica was 70% silica sol and 30% Aerosil 200.Iron nitrate was melted on a hotplate with a small amount of water.Then, in order, were added manganese, bismuth, cobalt and nickelnitrates, forming a solution that was added to the Mo--Cr--Si solutionpreviously prepared, forming a slurry which was heated on a hotplatewith stirring until it started to thicken. It was then dried at 120° C.,heated 3 hours at 290° C. and 3 hours at 425° C.

The composition was then ground to 20-35 mesh and heated for 3 hours at610° C. The catalyst composition was 50% Ni₂.5 Co₄.5 Fe₂ MnBiCr₀.5Mo₁₃.2 O_(x) +50%SiO₂.

EXAMPLE 18

A catalyst having the composition, 50% BiVO_(x) +25% SiO₂ +25%Al₂ O₃,was made as follows:

37.4 g of bismuth nitrate dissolved in dilute nitric acid (10%) wasadded to 9.0 g of ammonium metavanadate dissolved in hot water. 31.2 gof silica sol and 62.5 g alumina sol were added to this, and theresultant slurry was then worked up as in Example 17.

EXAMPLE 19

Bismuth nitrate dissolved in dilute nitric acid was mixed with asolution containing ammonium metavanadate and ammonium heptamolybdatedissolved in hot water. Silica sol and alumina sol were added to thisand the slurry was evaporated to near dryness over a hot plate. The drymaterial was heat treated at 290° C./3 hours, 425° C./3 hours, groundand screened to 20-35 mesh and heated at 610° C./3 hours. Thecomposition of the catalyst was 50% BiV₀.7 MoO_(x) +25% SiO₂ +25% Al₂O₃.

COMPOSITION OF CATALYST MIXTURES Mixture A

This is a mixture of the catalysts of Example 6 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture B

This is a mixture of the catalysts of Example 4 and Example 1 with aweight ratio of the latter of the former of 0.15.

Mixture C

This is a mixture of the catalysts of Example 7 and Example 1 with aweight ratio of the latter of the former of 0.15.

Mixture D

This is a mixture of the catalysts of Example 8 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture E

This is a mixture of the catalysts of Example 9 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture F

This is a mnixture of the catalysts of Example 5 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture G

This is a mixture of the catalysts of Example 14 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture H

This is a mixture of the catalysts of Example 15 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture I

This is a mixture of the catalysts of Example 3 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture J

This is a mixture of the catalysts of Example 13 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture K

This is a mixture of the catalysts of Example 10 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture L

This is a mixture of the catalysts of Example 12 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture M

This is a mixture of the catalysts of Example 16 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture N

This is a mixture of the catalysts of Example 11 and Example 1 with aweight ratio of the latter of the former of 0.15.

Mixture O

This is a mixture of the catalysts of Example 2 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture P

This is a mixture of the catalysts of Example 17 and Example 1 with aweight ratio of the latter to the former of 0.15.

Mixture Q

This is a mixture of the catalysts of Example 4 and Example 18 with aweight ratio of the latter to the former of 0.15.

Mixture R

This is a mixture of the catalysts of Example 4 and Example 19 with aweight ratio of the latter to the former of 0.15.

In the ammoxidation runs of the following examples summarized in Table1, the mixture of catalysts is in a tubular 3/8 inch I.D. stainlesssteel fixed bed reactor. To make the mixture of particulate catalysts,the desired weight of each of the two catalyst compositions is put in avial and shaken until uniformly dispersed before placing the desiredamount of the catalyst mixture in the reaction tube. The reactor isequipped with a preheat leg and is immersed in a temperature controlledmolten salt bath. The gaseous feed components are metered through massflow controllers into the bottom of the reactor through the preheat leg.Water is introduced through a septum at the top of the preheat leg,using a syringe pump. The feed is fed to the catalyst for a pre-run of 1hour before collection of product unless a longer pre-run time is noted;the runs of each example last 30-60 minutes during which the product iscollected for analysis. In the ammoxidation runs shown in Table 1 themolar ratios of propane:NH₃ :O₂ :H₂ O were 5/1/2/1.

In Table 1, Example 36 is a comparative run and is not an example of theinvention. Nor is catalyst mixture Q.

                                      TABLE 1                                     __________________________________________________________________________                           Propane: Mole %    % Selectivity                                     CT Percent                                                                             Conversion to      Based on Propane                         Catalyst                                                                           Temp,                                                                             Secs                                                                             Propane                                                                             (2)     AN +                                                                              (3)                                                                              AN +   AN +                                                                              AN +                         Example                                                                            Mixture                                                                            °C.                                                                        (4)                                                                              Conversion                                                                          AN  HCN HCN C.sub.3 =                                                                        C.sub.3 =                                                                         AN HCN C.sub.3                      __________________________________________________________________________                                                     =                            20(5)                                                                              A    470 1.7                                                                              11.8  6.7 1.0 7.7 0.9                                                                              7.5 56.6                                                                             65.3                                                                              63.9                         21(5)                                                                              B    470 1.5                                                                              12.3  7.5 0.7 8.2 0.8                                                                              7.3 61.0                                                                             66.6                                                                              67.3                         22(6)                                                                              C    470 2.2                                                                              12.6  6.8 0.7 7.5 1.2                                                                              7.9 53.6                                                                             58.8                                                                              62.8                         23   D    470 1.5                                                                              11.5  6.3 0.4 6.7 1.0                                                                              7.3 54.7                                                                             58.2                                                                              63.9                         24(7)                                                                              E    470 1.6                                                                              11.4  6.2 0.6 6.8 1.0                                                                              7.1 54.4                                                                             59.3                                                                              62.9                         25(6)                                                                              F    470 1.4                                                                              10.7  5.9 0.7 6.6 1.6                                                                              7.5 55.6                                                                             62.3                                                                              70.4                         26(1)(8)                                                                           G    470 1.6                                                                              12.4  6.6 1.3 7.9 0.6                                                                              7.2 53.1                                                                             63.7                                                                              58.1                         27(1)(7)                                                                           H    470 1.6                                                                              10.8  5.3 0.9 6.2 0.6                                                                              5.9 49.1                                                                             57.9                                                                              55.2                         28   I    470 1.6                                                                              11.6  6.5 0.6 7.1 1.0                                                                              7.5 55.5                                                                             60.4                                                                              64.0                         29(1)(8)                                                                           J    470 1.5                                                                              10.0  4.9 0.7 5.6 0.8                                                                              5.7 49.2                                                                             56.1                                                                              56.9                         30(7)                                                                              K    470 1.5                                                                              12.9  6.5 0.7 7.2 0.9                                                                              7.4 50.5                                                                             56.0                                                                              57.6                         31(1)(9)                                                                           L    470 1.5                                                                              10.3  5.4 0.7 6.1 0.6                                                                              6.0 52.3                                                                             58.9                                                                              58.6                         32(1)(9)                                                                           M    470 1.6                                                                              11.0  5.5 1.2 6.7 1.0                                                                              6.5 49.5                                                                             60.3                                                                              58.3                         33(5)                                                                              N    470 1.5                                                                              10.7  6.2 0.6 6.8 1.0                                                                              7.2 57.5                                                                             63.5                                                                              66.5                         34(6)                                                                              O    470 1.4                                                                              11.3  6.4 0.5 6.9 0.8                                                                              7.2 56.7                                                                             61.2                                                                              64.1                         35(7)                                                                              P    470 1.7                                                                              11.7  6.4 0.5 6.9 1.1                                                                              7.5 54.5                                                                             58.8                                                                              63.8                         36   Q    470 1.6                                                                              8.2   3.0 0.3 3.3 0.6                                                                              3.6 36.2                                                                             40.1                                                                              42.9                         37   R    470 1.6                                                                              6.7   3.9 0.3 4.2 0.5                                                                              4.4 59.1                                                                             64.2                                                                              66.3                         __________________________________________________________________________     (1) Catalyst Mixture was reduced for 15 min. at 470° C. with           NH.sub.3 before prerun.                                                       (2) AN is Acrylonitrile                                                       (3) C.sub.3 = is Propylene                                                    (4) Contact, Time, Seconds                                                    (5) The feed was fed to the reactor for 72 hrs before collecting product      for analysis.                                                                 (6) The feed was fed to the reactor for 48 hrs before collecting product      for analysis.                                                                 (7) The feed was fed to the reactor for 24 hrs before collecting product      for analysis.                                                                 (8) The feed was fed to the reactor for 96 hrs before collecting product      for analysis.                                                                 (9) The feed was fed to the reactor for 216 hrs before collecting product     for analysis.                                                            

As will be evident to those skilled in the art various modifications ofthis invention can be made or followed in the light of the foregoingdisclosure and discussion without departing from the spirit and scope ofthe disclosure or from the scope of the claims.

We claim:
 1. A process for the ammoxidation of a C₃ to C₅ paraffin to anα,β-unsaturated mononitrile which comprises contacting in a reactionzone said paraffin in the vapor phase in admixture with ammonia,molecular oxygen, and optionally an inert gaseous diluent, with anintimate particulate mixture of a first catalyst composition and asecond catalyst composition, said feed to the reaction zone containing amole ratio of paraffin:NH₃ in the range of 2 to 16, and a mole ratio ofparrafin:O₂ in the range from 1 to 10 said first catalyst compositionbeing 0-99 weight percent of a diluent/support and 100-1 weight percentof a catalyst having oxygen and the cation components in the proportionsindicated by the empirical formula:

    Bi.sub.a V.sub.b L.sub.l M.sub.m T.sub.t O.sub.x,          formula (1)

wherein L is one or more of K, Cs, Rb and Tl; M is one or more of Mo, W,Cr, Ge, Sb, Sn, P, Pb and B; T is one or more of Zn, Nb, Ta, Fe, Co, NiCu, Mn, Ti and rare earths, a=1-25 b=1-50 l=0-1 m=0.1-20 t=0-20 x isdetermined by the oxidation state of the other elements in the catalyst,(a+b):(l+m+t)=20:1 to 1:5 a:b=1:5-5:1with the proviso that the atomicratio of Mo:V is zero to <10; said second catalyst composition being0-99 weight percent of a diluent/support and 100-1 weight percent of acatalyst having oxygen and the cation components in the proportionsindicated by the empirical formula:

    Bi.sub.k Fe.sub.l Mo.sub.12 V.sub.v D.sub.d E.sub.e F.sub.f G.sub.g O.sub.x formula ( 2)

where D is one or more of an alkali metal, Sm, Ag E is one or more ofMn, Cr, Cu, Zn, Cd, La, F is one or more of P, As, Sb, Te, W, B, Sn, Pb,Se G is one or more of Co, Ni, alkaline earth metal, and k is 0.1-12, lis 0.01-12, v is 0-0.5, d is 0-0.5, e is 0-10, f is 0-10, g is 0-12,v+k+l+d+e+f+g≦24, and x is a number determined by the valencerequirements of the other elements present, wherein the weight ratio insaid mixture of said first catalyst composition to said second catalystcomposition is in the range of 0.001 to 2.5.
 2. A process of claim 1wherein said mole ratio of paraffin:NH₃ is in the range from 3 to
 7. 3.A process of claim 1 wherein said mole ratio of paraffins:O₂ is in therange from 1.5 to
 5. 4. A process of claim 2 wherein said mole ratio ofparaffin:O₂ is in the range from 1.5 to
 5. 5. A process according toclaim 1 wherein the mole ratio of O₂ to NH₃ in the feed to the reactionzone is in the range from 1 to
 10. 6. A process according to claim 1wherein the mole ratio of inert gaseous diluent to paraffin in the feedto the reaction zone is in the range from zero to
 5. 7. A process ofclaim 1 wherein said paraffin is propane or isobutane.
 8. A process ofany one of any one of claim 1 wherein said paraffin is propane.
 9. Aprocess of claim 2 wherein said paraffin is propane or isobutane.
 10. Aprocess of claim 4 wherein said paraffin is propane.